r260650 - in /trunk/gcc/ada: ChangeLog exp_ch7.adb

[pmderodat@gcc.gnu.org]

Author: pmderodat
Date: Thu May 24 13:05:08 2018
New Revision: 260650

URL: https://gcc.gnu.org/viewcvs?rev=260650&root=gcc&view=rev
Log:
[Ada] Memory leak mixing limited and nonlimited functions

This patch fixes a memory leak. If a build-in-place function with a result
whose size is not known at the call site is called, and that function calls a
non-build-in-place function that allocates on the secondary stack, the
secondary stack was not necessarily cleaned up, which caused a memory leak.

The following program should print:
"Current allocated space :  0 bytes"
(among other things) in the loop.

./bip_leak-main > log
grep 'Current allocated' log
  Current allocated space :  0 bytes
  Current allocated space :  0 bytes
  Current allocated space :  0 bytes

with Ada.Finalization;
package BIP_Leak is
   subtype Limited_Controlled is Ada.Finalization.Limited_Controlled;

   type Nonlim_Controlled is new Ada.Finalization.Controlled with null record;
   type Needs_Fin is record
      X : Nonlim_Controlled;
   end record;

   type Lim_Controlled is new Limited_Controlled with null record;

   function Return_Lim_Controlled (Source : Boolean)
                       return Lim_Controlled;

   procedure Dump_SS;

end BIP_Leak;

with Ada.Text_IO;
pragma Warnings (Off);
with System.Secondary_Stack;
pragma Warnings (On);
package body BIP_Leak is
   function Transform (X : Needs_Fin) return Lim_Controlled is
   begin
      return (Limited_Controlled with null record);
   end;

   function Return_Needs_Fin (I : Boolean) return Needs_Fin is
     THR : Needs_Fin;
   begin
      return THR;
   end;

   function Return_Lim_Controlled (Source : Boolean)
                       return Lim_Controlled is
   begin
      return Transform (Return_Needs_Fin (Source));
   end Return_Lim_Controlled;

   procedure Dump_SS_Instance is
     new System.Secondary_Stack.SS_Info (Ada.Text_IO.Put_Line);
   procedure Dump_SS renames Dump_SS_Instance;

end BIP_Leak;

procedure BIP_Leak.Main is
begin
   for Count in 1 .. 350_000 loop
      declare
         Msg : constant Lim_Controlled := Return_Lim_Controlled (True);
      begin
         if Count mod 100_000 = 0 then
            Dump_SS;
         end if;
      end;
   end loop;
end BIP_Leak.Main;

2018-05-24  Bob Duff  <duff@adacore.com>

gcc/ada/

	* exp_ch7.adb (Expand_Cleanup_Actions): Create a mark unconditionally
	for build-in-place functions with a caller-unknown-size result.
	(Create_Finalizer): For build-in-place functions with a
	caller-unknown-size result, check at run time whether we need to
	release the secondary stack.

Modified:
    trunk/gcc/ada/ChangeLog
    trunk/gcc/ada/exp_ch7.adb